The statements in this section merely provide background information related to the present disclosure. Accordingly, such statements are not intended to constitute an admission of prior art.
Powertrain systems may be configured to transfer torque originating from multiple torque-generative devices through a torque transmission device to an output member that may be coupled to a driveline. Such powertrain systems include hybrid powertrain systems and extended-range electric vehicle systems. Control systems for operating such powertrain systems operate the torque-generative devices and apply torque transfer elements in the transmission to transfer torque in response to operator-commanded output torque requests, taking into account fuel economy, emissions, drivability, and other factors. Exemplary torque-generative devices include internal combustion engines and non-combustion torque machines. The non-combustion torque machines may include electric machines that are operative as motors or generators to generate a torque input to the transmission independently of a torque input from the internal combustion engine. The torque machines may transform vehicle kinetic energy transferred through the vehicle driveline to electrical energy that is storable in an electrical energy storage device in what is referred to as a regenerative operation. A control system monitors various inputs from the vehicle and the operator and provides operational control of the hybrid powertrain, including controlling transmission operating state and gear shifting, controlling the torque-generative devices, and regulating the electrical power interchange among the electrical energy storage device and the electric machines to manage outputs of the transmission, including torque and rotational speed.
It is known, for example, to require an electrical energy storage device in a hybrid powertrain to sustain electrical loads during operation in neutral. These electrical loads can include auxiliary loads such as an air conditioner or entertainment system of the vehicle. One drawback can be an inability to charge the electrical energy storage device during operation in neutral using torque provided from the engine when the powertrain lacks a mechanical disconnect from a driveline. In some instances, the vehicle can be required to operate in neutral for extended periods of time, such as when the vehicle is in a car wash. Accordingly, when the state of charge of the electrical energy storage device depletes from sustaining these electrical loads during operation in neutral for an extended period of time, the hybrid powertrain can be commanded to shut down.